Described on US eBay as an Extremely Rare Rokon 340 Automatic Flat Track Racer, we understand this bike was part of Dan Rouit's Flat Track museum, before he passed away. Now it's in Wisconsin.
The advert states it's '1 of 33 Factory Built Flat Track Machines' built by Rokon, who were better known for their huntin', shootin', fishin' two-wheel-drive utility bikes.
The advert also adds the bike hasn't run since being restored and is powered by a 'Sachs 340cc 2-Stoke Engine and a Torque Converter Drive.'
Thanks to Damon York for the tip-off.